Influence of translational and internal energy upon the chemiluminiscent part of the exothermic reaction NO + O3 → NO*2 + O2 → NO2 + hν + O2
1980; Elsevier BV; Volume: 45; Issue: 1 Linguagem: Inglês
10.1016/0301-0104(80)85168-8
ISSN1873-4421
Autores Tópico(s)Plasma Applications and Diagnostics
ResumoThe influence of internal (rotational and electronic fine structure states of NO) and translational energy upon the chemicaluminescence has been studied by crossing a seeded NO beam with an effusive O3 beam for energies large in comparison with threshold. The translational energy (0.4< Etr< 1.6 eV) is selected by a velocity selector placed in front of the scattering region. Thus, the internal beam temperature (state distribution) remains constant, when Etr is varied by changing the rotational frequency of the velocity selector. The cross section of this exothermic process is found to increase very rapidly with translation, νhν ∝ E3.75tr, with some levelling off starting at Etr ≈ 1.2 eV. The influence of the internal energy of the NO-molecules is studied by changing the pressure behind the nozzle, at a constant speed of the velocity selector; thereby the internal beam temperature is varied (100 ⩽ T| ⩽ 300 K). A linear behaviour is found: σhν ∝ [1+α(kT|/Ethreshold)] with Ethreshold=0.129 eV and α = 4.5 ± 0.5 for Etr between 0.62 and 0.84 eV. Assuming the rotational and electronic fine structure temperature equal to T|. we obtain (dohν/dĒt)/(dσhν/dĒtr) = 4.5 ± 0.5 at Etr = 0.7 eV with Ēint = Ērot + Ēel· Eint is even more efficient than Etr in promoting chemiluminescence in the visible. If the internal energy effect can be attributed ot different cross sections for the two fine structure states involved, one derives σhν(Π12)/σhν(Π32) = 0.27 ± 0.03. The exothermic chemiluminescent reaction cross section is surprisingly energy selective far from the threshold.
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